Serial scan designs are used to access the functionality of targeted electrical circuitry for emulation and test purposes. Such scan designs typically include a plurality of serially connected shift elements. Each shift element is operatively associated with a predetermined node of the target circuit to provide access to that node for emulation and/or test purposes. This type of arrangement disadvantageously requires a one-to-one ratio of shift elements to accessed nodes.
It is therefore desirable to provide a scan design which can access a given number of nodes without requiring a one-to-one ratio of shift elements to accessed nodes.
The present invention provides the aforementioned desirable scan design using circuitry that permits a shift element to selectively access more than one node of the target circuit.